Trade fraud, smuggling, and terrorism have increased the need for non-intrusive inspection systems such as X-ray, gamma ray and linear accelerator (LINAC)-based systems for inspecting cargo, trucks, passenger vehicles, and other transportation systems, which efficiently provide for the movement of commodities across borders. In addition, they provide opportunities for the inclusion of contraband items such as weapons, explosives, illicit drugs and precious metals. In particular, non-intrusive inspection systems are used in applications ranging from curbside inspection of parked vehicles to scanning in congested or high traffic ports. The term port, while generally accepted as referring to a seaport, also applies to a land border crossing or any port of entry.
The size of the cargo or vehicle under inspection generally determines the size of the imaging system and thus, in general the bigger the object under inspection, the bigger the inspection system.
With an increase in global commerce, port authorities require additional sea berths and associated container storage space. Additional space requirements are typically met by the introduction of higher container stacks, an expansion of ports along the coastline, or by moving inland. However, these scenarios are not typically feasible. Space is generally in substantial demand and short supply. Existing ports operate under a routine that is not easily modified without causing disruption to the entire infrastructure of the port. The introduction of new procedures or technologies often requires a substantial change in existing port operating procedures in order to contribute to the port's throughput, efficiency, and operability.
With limited space available and a need to expand for increased inspection performance, finding suitable space to accommodate additional inspection facilities along the normal process route remains difficult. Moreover, systems incorporating the high energy X-ray sources, or linear accelerators (LINAC), require either a major investment in shielding material (generally in the form of concrete formations or buildings) or the use of exclusion zones (dead space) around the building itself. In either case, the building footprint is significant depending upon the size of cargo containers to be inspected. Thus, the continual conflict is between making the system as small as possible while capable of inspecting a varying range of objects, including large objects.
A typical size range for objects under inspection includes vehicles as small as compact automobiles (or even smaller) to trucks carrying large containers. Thus, the object under inspection typically ranges from a compact automobile as small as 1.2 meters wide by 1.2 meters high to a large truck that is up to 3 meters wide and 4.6 meters high.
Therefore, there is a need for a relatively compact inspection system that produces at least one image of objects of varying sizes. What is also needed is a relatively compact inspection system that is capable of producing an image of an object in a single, first-pass image scan with no corner cut-off for smaller vehicles.
What is also needed is a relatively compact inspection system that is capable of producing an image of a large object in a multiple pass image scan in situations where a first pass image scan does not produce an image of a large object under inspection without corner cut off.
What is also needed is a relatively compact multiple pass inspection system that maintains overall inspection throughput.